The words xero-, zero sound the same but have different meanings and spellings. Why do xero-, zero sound the same even though they are completely different words?
The answer is simple: xero-, zero are homophones of the English language.
Forms terms relating to dry- or dryness
Forms terms relating to Xerox photocopying
The numerical symbol 0; a cipher.
Mathematics The identity element for addition.
Mathematics A cardinal number indicating the absence of any or all units under consideration.
Mathematics An ordinal number indicating an initial point or origin.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.